2.2.0.25falsefalse007050 - Disclosure - Fair Value Measurements and Disclosures (Policies)truefalsefalse1falsefalseUSDfalsefalse1/1/2011 - 3/31/2011
USD ($)
USD ($) / shares
$c20110101to20110331http://www.sec.gov/CIK0000072207duration2011-01-01T00:00:002011-03-31T00:00:00U003Standardhttp://www.xbrl.org/2003/instancesharesxbrli0U001Standardhttp://www.xbrl.org/2003/iso4217USDiso42170U002Dividehttp://www.xbrl.org/2003/iso4217USDiso4217http://www.xbrl.org/2003/instancesharesxbrli0U004Standardhttp://www.xbrl.org/2003/instancepurexbrli0USDUSD$2true0nbl_NotesToFinancialStatementsAbstractnblfalsenadurationNo definition available.falsefalsefalsefalsefalsefalsefalsefalsefalsefalse1falsefalsefalse00falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringNo definition available.falsefalse3false0nbl_FairValueOfFinancialInstrumentsMeasuredRecurringBasisPolicynblfalsenadurationDescribes an entity's accounting policy for determining the fair value of its financial instruments, measured on a recurring...falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00<div><div align="left" style="text-indent: 0pt; display: block; margin-left: 0pt; margin-right: 0pt;"><font style="display: inline; font-family: Times New Roman; font-size: 10pt; font-weight: bold;">Assets and Liabilities Measured at Fair Value on a Recurring Basis</font></div><div align="justify" style="text-indent: 0pt; display: block; margin-left: 0pt; margin-right: 0pt;"> </div><div align="left" style="text-indent: 0pt; display: block; margin-left: 0pt; margin-right: 0pt;"><font style="display: inline; font-family: Times New Roman; font-size: 10pt;">Certain assets and liabilities are measured at fair value on a recurring basis in our consolidated balance sheets.  The following methods and assumptions were used to estimate the fair values:  </font></div><div align="justify" style="text-indent: 0pt; display: block; margin-left: 0pt; margin-right: 0pt;"> </div><div align="left" style="text-indent: 0pt; display: block; margin-left: 0pt; margin-right: 0pt;"><font style="display: inline; font-family: Times New Roman; font-size: 10pt;"><font style="font-style: italic; display: inline;">Cash, Cash Equivalents, Accounts Receivable and Accounts Payable</font><font style="font-style: italic; display: inline;"> </font> The carrying amounts approximate fair value due to the short-term nature or maturity of the instruments. </font></div><div align="justify" style="text-indent: 0pt; display: block; margin-left: 0pt; margin-right: 0pt;"> </div><div align="left" style="text-indent: 0pt; display: block; margin-left: 0pt; margin-right: 0pt;"><font style="display: inline; font-family: Times New Roman; font-size: 10pt;"><font style="font-style: italic; display: inline;">Mutual Fund Investments  </font> Our mutual fund investments, which primarily include assets held in a rabbi trust, consist of various publicly-traded mutual funds that include investments ranging from equities to money market instruments. The fair values are based on quoted market prices for identical assets.</font></div><div align="justify" style="text-indent: 0pt; display: block; margin-left: 0pt; margin-right: 0pt;"> </div><div align="left" style="text-indent: 0pt; display: block; margin-left: 0pt; margin-right: 0pt;"><font style="display: inline; font-family: Times New Roman; font-size: 10pt;"><font style="font-style: italic; display: inline;">Commodity Derivative Instruments   </font>Our commodity derivative instruments consist of variable to fixed price commodity swaps, two-way and three-way collars and basis swaps. We estimate the fair values of these instruments based on published forward commodity price curves as of the date of the estimate. The discount rate used in the discounted cash flow projections is based on published LIBOR rates, Eurodollar futures rates and interest swap rates. The fair values of commodity derivative instruments in an asset position include a measure of counterparty nonperformance risk, and the fair values of commodity derivative instruments in a liability position include a measure of our own nonperformance risk, each based on the current published credit default swap rates. In addition, for collars, we estimate the option values of the put options sold (for three-way collars) and the contract floors and ceilings (for two-way and three-way collars) using an option pricing model which takes into account market volatility, market prices and contract terms. See Note 4. Derivative Instruments and Hedging Activities.</font></div><div align="justify" style="text-indent: 0pt; display: block; margin-left: 0pt; margin-right: 0pt;"> </div><div align="left" style="text-indent: 0pt; display: block; margin-left: 0pt; margin-right: 0pt;"><font style="display: inline; font-family: Times New Roman; font-size: 10pt;"><font style="font-style: italic; display: inline;">Interest Rate Derivative Instrument   </font>We estimate the fair value of our forward starting swap based on published interest rate yield curves as of the date of the estimate. The fair values of interest rate derivative instruments in an asset position include a measure of counterparty nonperformance risk, and the fair values of interest rate derivative instruments in a liability position include a measure of our own nonperformance risk, each based on the current published credit default swap rates. See Note 4. Derivative Instruments and Hedging Activities.</font></div><div align="justify" style="text-indent: 0pt; display: block; margin-left: 0pt; margin-right: 0pt;"> </div><div align="left" style="text-indent: 0pt; display: block; margin-left: 0pt; margin-right: 0pt;"><font style="display: inline; font-family: Times New Roman; font-size: 10pt;"><font style="font-style: italic; display: inline;">Deferred Compensation Liability </font>  The value is dependent upon the fair values of mutual fund investments and shares of our common stock held in a rabbi trust.<font style="font-style: italic; display: inline;"> See Mutual Fund Investments </font>above<font style="font-style: italic; display: inline;">.</font></font></div></div>Assets and Liabilities Measured at Fair Value on a Recurring Basis Certain assets and liabilities are measured at fair value on a recurring basis in ourfalsefalsefalsefalsefalseOtherxbrli:stringItemTypestringDescribes an entity's accounting policy for determining the fair value of its financial instruments, measured on a recurring basis.No authoritative reference available.falsefalse4false0nbl_FairValueOfFinancialInstrumentsMeasuredNonrecurringBasisPolicynblfalsenadurationDescribes an entity's accounting policy for determining the fair value of its financial instruments, measured on a...falsefalsefalsefalsefalsefalsefalsefalsefalsefalseverboselabel1falsefalsefalse00<div><div align="justify" style="text-indent: 0pt; display: block; margin-left: 0pt; margin-right: 0pt;"> </div><div align="left" style="text-indent: 0pt; display: block; margin-left: 0pt; margin-right: 0pt;"><font style="display: inline; font-family: Times New Roman; font-size: 10pt;">Certain assets and liabilities are measured at fair value on a nonrecurring basis in our consolidated balance sheets.</font></div><div align="justify" style="text-indent: 0pt; display: block; margin-left: 0pt; margin-right: 0pt;"> </div></div> Certain assets and liabilities are measured at fair value on a nonrecurring basis in our consolidated balance sheets. falsefalsefalsefalsefalseOtherxbrli:stringItemTypestringDescribes an entity's accounting policy for determining the fair value of its financial instruments, measured on a Nonrecurring basis.No authoritative reference available.falsefalse13Fair Value Measurements and Disclosures (Policies)UnKnownUnKnownUnKnownUnKnownfalsetrue